Printed Circuit Boards (PCBs) have become increasingly complex assemblies. As a result of this increased complexity, PCBs are difficult to analyze in case of a failure. Part of this is due to the fact that a PCB can contain several devices and busses that run asynchronously with respect to each other and also run at different clock speeds. One particular type of failure that can be difficult to detect and to verify has to do with clock circuitry. This is especially true for an intermittent clock failure due to a poor connection, improper termination or a faulty device that may be slightly off frequency or has a tendency to frequency drift under certain conditions (temperature, humidity, etc).
One way to attempt to diagnose these clock failures is to use a frequency counter, but unless the frequency counter is being employed at the time the failure occurs, detection of a failure can be difficult. Use of an oscilloscope or other type of measuring device also may not provide the level of precision required to determine if a clock circuit occasionally drops a cycle or drifts off frequency for a period of time or under certain conditions.